Influence of in vivo or vitro microenvironment on the mechanical properties and histological structure of tissue engineered cartilage

Abstract

To investigate the influence of in vivo or vitro microenvironment on the mechanical properties and histological structure of tissue engineered cartilage, and to provide the appropriate parameters for cartilage construct in vitro. Human fetal articular chondrocytes were cultured and expanded in vitro, the passage 2 chondrocytes were seeded at the density of 6 x 10(7) cells/cm3 to cylindric dimensional scaffolds made by polyglycolic acid (PGA) and polylactic acid (PLA). These constructs were cultured in vitro for 4 weeks. After 4 weeks, part of samples were implanted subcutaneously into nude mice for 6 and 12 weeks, the others continued to be cultured in vitro. All specimens were harvested after 6 and 12 weeks, and evaluated by gross observation, histology, histochemistry, ultrastructure and mechanical test. All specimens in vivo and vitro eventually formed good shape hyaline cartilage. The constructs in vivo group was white color with smooth surface, and had better mechanical properties than those in vitro, by TEM we can observe the thick and striated collagen fibers in regularly arranged collagen fibril which was similar to adult articular cartilage. The constructs in vitro group was yellow color with coarse surface, the appearance and ultrastructure was similar to fetal articular cartilage. Specimens implanted for 12 weeks in vivo had better compressive modulus(38.28 +/- 3.95) MPa and collagen diameter (41.58 +/- 2.78) nm than those cultured in vitro at the same time (4.12 +/- 0.63) MPa, (15.83 +/- 1.70) nm (P < 0. 01). The structure and function of human tissue engineered cartilage became mature gradually from vitro to vivo, thick and striated collagen fibrils net similar to adult articular cartilage can be formed in constructs of vivo group,increased collagen cross-linking might be the reason that their mechanical properties been greatly improved.